stack/slapos: use slapos.rebootstrap in any SR but use a dedicated rebootstrap...

stack/slapos: use slapos.rebootstrap in any SR but use a dedicated rebootstrap directory in component/slapos only.

because only component/slapos can be build with the different python version than 2.7.

component/slapos/buildout.cfg

@@ -28,8 +28,7 @@ parts =
   py
   firewalld-patch
 
-extensions +=
-  slapos.rebootstrap
+rebootstrap-directory = rebootstrap
 
 [environment]
 # Note: For now original PATH is appended to the end, as not all tools are
@@ -124,6 +123,3 @@ eggs =
     ${slapos:eggs}
 interpreter = py
 scripts = py
-
-[versions]
-slapos.rebootstrap = 3.7

stack/slapos.cfg

@@ -10,6 +10,7 @@ python = python2.7
 # checkout, you must add both slapos-cookbook-develop and slapos-cookbook in parts
 
 extensions +=
+  slapos.rebootstrap
   slapos.extension.strip
 
 show-picked-versions = true
@@ -138,6 +139,7 @@ slapos.cookbook = 1.0.48
 slapos.core = 1.3.18
 slapos.extension.strip = 0.2
 slapos.libnetworkcache = 0.14.5
+slapos.rebootstrap = 3.8
 slapos.recipe.build = 0.32
 slapos.recipe.cmmi = 0.4
 stevedore = 1.21.0